PIMR, a novel Kunitz-type protease inhibitor from the Macrovipera razii, with dual anticoagulant and anticancer activities.

Snake venom is a rich source of bioactive peptides with diverse pharmacological effects. Kunitz-type protease inhibitors are one of the multifunctional peptides isolated from the snake venom. The Razi's viper, Macrovipera razii, is a species endemic to Iran whose venom components are still largely unexplored. In this study, we report the isolation, cloning, and functional characterization of PIMR, a novel Kunitz-type protease inhibitor derived from M. razii venom. The gene encoding PIMR was amplified from venom gland cDNA and then cloned into a prokaryotic expression vector. The PIMR protein consists of 71 residues stabilized by three disulfide bonds, characteristic of the folded Kunitz domain. Recombinant PIMR was expressed in Escherichia coli and purified by affinity chromatography. The anticoagulant activity of PIMR was assessed by clotting time, prothrombin time, and activated partial thromboplastin time assays. The results indicated a dose-dependent anticoagulant activity of the peptide. The PIMR also exhibited anticancer effects against the highly invasive breast cancer cell line, MDA-MB-231, with an IC50 of 33 μg/μl. Docking studies indicated that the RGN motif of PIMR interacts with integrins, suggesting a potential mechanism for inhibiting cancer cell proliferation. Additionally, molecular docking confirmed binding of PIMR to trypsin, supporting its role as a serine protease inhibitor. Our findings establish PIMR as a novel serine protease inhibitor with promising anti-coagulant and anti-cancer properties. PIMR, with its diverse biological functions, represents a potential candidate for drug development and further molecular investigations.